Obstructive Sleep Apnea

Obstructive Sleep Apnoea

Written by Dr Andrew Lam

Diagnosis and Severity of OSA

OSA confirmed by sleep study by the apnoea hypopnoea index (AHI), which represents the number of apnoeas/hypopnoeas detected in 1 hour. 

Diagnosis of OSA made if: 

AHI > 15 in an asymptomatic patient

AHI > 5 in symptomatic patient

Mild OSA: AHI > 5 but < 15

Moderate OSA: AHI > 15 but < 30

Severe OSA: AHI > 30 

Epworth Sleepiness Scale

In the following situations, how likely are you to fall asleep?

0 – No chance

1 – Slight chance

2 – Moderate chance

3 – High chance

0-7: Unlikely to be abnormally sleepy

8-9: Average amount of daytime sleepiness

10-15: May be excessively sleepy depending on the situation. Consider seeking medical attention

16-24: Excessively sleepy and should consider seeking medical attention.

STOP-BANG Questionnaire

S – Snoring? (Can be heard through closed doors) 

T – Tired? (Feel tired, sleepy or fatigued in the daytime)

O – Observed choking/gasping in sleep?

P – Pressure (Treated for or have hypertension)

B – BMI > 35?

A – Age > 50?

N – Neck size (Collar size >40cm)

G – Gender? (Male at higher risk) 

Low Risk: Score 0-2

Intermediate Risk: Score 3-4

High Risk: Score 5-8

Complications

Cardiovascular: Hypertension, LV Failure/Hypertrophy, Myocardial Ischaemia, Arrhythmias. 

Thought to be secondary to a combination of hypoxia/hypercapnia and episodes of sympathetic drive/oxidative stress associated with this. 

Pulmonary: Pulmonary hypertension and subsequent right sided heart strain/failure. Thought to be due to reflexive pulmonary vasoconstriction during episodes of hypoxis

Neuropsychiatric: Decreased executive and cognitive function, mood disorders, psychosis, memory deficits